Provided is a charged particle beam microscope which has a small mechanical vibration amplitude of a distal end of an emitter tip, is capable of obtaining an ultra-high resolution sample observation image and removing shaking or the like of the sample observation image. A gas field ion source includes: an emitter tip configured to generate ions; an emitter-base mount configured to support the emitter tip; a mechanism configured to heat the emitter tip; an extraction electrode installed to face the emitter tip; and a mechanism configured to supply a gas to the vicinity of the emitter tip, wherein the emitter tip heating mechanism is a mechanism of heating the emitter tip by electrically conducting a filament connecting at least two terminals, the terminals are connected by a V-shaped filament, an angle of the V shape is an obtuse angle, and the emitter tip is connected to a substantial center of the filament.